The Fuse Holders Wouldn’t Hold

Several years ago, I noticed that the radiator cooling fans (all three of them) on my Lotus Esprit S2 seemed to be operating at suboptimal speed. With a fiberglass-bodied car, this problem is often caused by a dodgy ground connection. Since there's no handy metal chassis to find, it's necessary to run ground wires everywhere -- which is how the factory designed the harness.

I found that the voltage was low, but all the grounds checked out. Checking this was much easier said than done. When I searched for the fan control relays, I found them nestled up under an inner fender. To assure that the relay wasn't damaged by a seized fan bearing, each relay had been duly equipped with its own fuse.

So far, so good. The fuses were all good. In checking them, however, I noticed that they were the European style, consisting of a ceramic mandrel with a die-cut piece of copper over it, forming the fuse element and the two contacts.

This is a simple two-part solution to the four-part (plus solder) design used in period autos -- a ceramic or glass tube with a fusible element and two end caps. But the fuses themselves were not the root of the problem. It was the Lucas relay-cum-fuse holder.

The fuse holder consisted of two rather stiff brass tabs protruding from the top of the relay, with holes in them designed to cup the pointed ends of the fuse. The trouble was there was little to no spring to the tabs. Thus, once a fuse was installed, it was inevitably a little loose. A firm contact was nigh impossible to achieve with the combination of marginal design and poor choice of materials. So, with use and time, the already dodgy connections degraded, and voltage at the load was compromised.

Since the relays were in a hard-to-see location, it was easy to solder the short pigtails of an inline fuse holder to each of the tabs and put in a proper fuse. The fans experienced a remarkable rejuvenation of operation, moving at least twice as much air and doing a proper job for the first time in years.

This entry was submitted by Peter Blackford and edited by Rob Spiegel.

Peter Blackford is a graduate of Worcester Polytechnic Institute and works as a design and applications engineer with Cable USA in Naples, Fla.

Yes, Tekochip, this must have been hard to track down. And I'll bet this was a problem for many of those who owned this car. A simple change in the fuse holder selection would have saved a lot of trouble.

This story reminds me of a joke that I got from a British electrical engineer a few years back. The question had arisen as to why the British drank their beer rather warmer than we do here in the states. The engineer explained that "It is because so many people have Lucas refrigerators." I have not been able to verify the validity of that assertion, but it was quite an interesting testament about the perceived quality of the product line.

I would also offer an opinion about installing any kind of unprotected fuseholder under the hood, which is that it is always an example of very poor engineering. In my part of the world, southeastern Michigan, the entire underhood area is subject to salt spray far more brutal than the military salt spray test. This is not something new, it has been that way for at least 50 years that I have been aware of it.

Hey William K, there are a couple theories about warm beer. One is simply that there is more flavor at warmer temps. In the past Americans favored bland beers, so the ice cold temp didn't kill the flavor. That's changed of course, and now Americans actually like tasty beer, maybe warmer beer will come to America.

Yes, I agree this must have been difficult to track down. Problems like these confound the best mechanics and are responsible for inordinate amounts of labor time. They're also responsible for people giving up on their cars before their time is really up.

Not for nothing has a leading UK motoring journalist (aka Jeremy Clarkson, aka "that insufferable prat" ) named Lucas "the prince of darkness". Reliability of British built cars in the 70's and 80's has always been a bit of a joke. Eventually the UK stopped making cars on their own initiative, letting the Japanese teach them how to build Nissans, and selling Jaguar to the Indians (Tata), Rolls Royce and Bently to the Germans (VW and BMW) and Rover to the Chinese (MG, or Rowei).

William, please bear in mind that the subject Lotus is mid-engined, thus "under the edge f the inner front fender", while technically "under the hood" (bonnet, in the UK), is far removed from the heat and other aspects typical of proximity to the engine.

Colin Chapman had one overriding design philosophy which, in this case and perhaps a few others, worked to his detriment: No component was allowed to do only one job. Thus he was probably thrilled with the concept of integrating the fuse holder with the relay. Had the concept been soundly executed, a great idea; but in the implemented design, not so much...

At least with the modification, that 'integration' is to a certain extent maintained, and the in-line fuse holders are actually much more 'sealed' than their predecessors which featured totally unprotected contacts.

Everyone thinks that Lucas had a quality problem... They were just ahead of their time. It is called "Planned Obsolescence" an Idea that the various US manufacturers have plyed with to varying degrees of success or failure. Though for the British motor industry, the standardization to Lucas parts made the problems universal rather than manufacturer specific. It is interesting that this "single vendor" mentality had a large part in the ending of "The British Auto Industry". When Leyland bought the sole company doing sheet metal bodywork it just finished it off...

Probably the only thing that has kept the US auto industry going is that the market is large enough that the individual car companies can support the multiple supply chains so every car doens't have exactly the same problem. And because of this there is some competition because there is something to compare your car against, as the different vendors don't all have the same design weaknesses.

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